瓜子金於不同海拔之表型可塑性與在地適應表現

Abstract

海拔梯度所形成的異質生態環境形成自然選擇的差異，促使物種跨海拔分布，表現較大的表型變異以適應不同環境。表型特徵受環境與基因型及其交互作用所影響，在不同環境中會因遺傳因子或表型可塑性等機制使表型發生變化。本研究以廣泛分布於台灣各海拔的瓜子金 (Polygala japonica Houtt.)為材料，該物種在不同海拔間呈現明顯的形態差異。透過收集各海拔與不同棲地共12個族群的種子，進行低海拔與高海拔地區的共園實驗與移地互換實驗。利用R統計軟體分析比較了各族群於原生地及試驗地的功能性狀變化、發芽表現與存活情況，以確認表型可塑性及在地適應對各海拔族群的影響程度，進一步了解瓜子金廣泛分布各海拔的原因與其生態策略。 研究結果顯示，瓜子金於原生地棲地環境相當多元，並呈現明顯的種內變異，並具有改變性狀適應當地環境的能力。該物種具較長的葉片壽命與發達的根系，多項性狀特徵受到表型可塑性與遺傳因素的共同影響，儘管遺傳因子影響尚待釐清，但兩處試驗地的環境差異對部分性狀仍具一定影響，並表現出不同的生態策略。在早期與後期生命史階段，瓜子金能根據環境變化調整性狀，進一步證明其適應不同環境的潛力，也解釋了該物種能在廣泛的海拔範圍內分布的原因。

Heigh heterogeneous environments formed by altitude gradient lead to differences in natural selection, prompting species to distribute across altitudes, exhibiting significant phenotypic variations to adapt to different environments. Phenotype is the traits affected by environment, genotype and interaction, and will respond to different environments due to mechanisms such as genetic factors or phenotypic plasticity. Polygala japonica Houtt. is a widely distributed perennial herb that has different morphological traits with different altitudes in Taiwan. We collected seeds from 12 populations with different altitudes and habitats, conducted in reciprocal transplant experiments at the low and high altitudes sites. We measured the functional traits, germination percentage and survival analysis in different populations, and all data analyzed within the R environment. In this study, we try to elucidate the effect of phenotypic plasticity and local adaptation, the ecological strategy with different altitudes in Polygala japonica. Our results showed that native habitat diversity and significant intraspecific variation of P. japonica has the ability to change traits to adapt the environmental conditions. The species has longer leaf lifespans and well-developed tap root, and other trait characteristics effected by both phenotypic plasticity and genetic factors. Though the impact of genetic factors still unknown, the environmental differences between the two experimental sites have certain effects on some traits, demonstrating different ecological strategies. On early and later life history stages, P. japonica can change traits according to environments, which further demonstrates its potential to adapt to different environments and explains why this species can be distributed in a wide altitude range.